In this study, we characterized and quantified vitamin B12 in canned apple snails, escargots, boiled plain using a microbiological assay based on Lactobacillus delbrueckii ATCC 7830. Vitamin B12 contents of canned escargots boiled plain were varied from approximately 0.8 μg-100g weight to approximately 5.5 μg-100g weight mean values, 2.2 μg-100g weight. We identified vitamin B12 compounds from escargots using liquid chromatography-electrospray ionization-tandem mass spectrometry. We found that escargots contained true vitamin B12 and two inactive corrinoids, which were identified as factor IIIm or methoxymensimidazolyl cyanocobamide, and factor S or 2-methylmercaptoadenyl cyanocobamide. These results indicate that canned escargots boiled plain are not good sources of vitamin B12 for humans.